1. Field of the Invention
The present invention pertains to a friction clutch, comprising a housing arrangement and a pressure plate arrangement, which is held by at least one leaf spring arrangement with freedom of axial movement with respect to the housing arrangement. The at least one leaf spring arrangement is fixed by a first attachment area to a first fastening area on the pressure plate assembly and by a second attachment area to a second fastening area on the housing arrangement.
2. Description of the Related Art
A pressure plate assembly of this type is known from, for example, DE 198 48 582. An axial view of a pressure plate assembly of this type is shown schematically in FIG. 1. This pressure plate assembly comprises a housing arrangement 12, which can be fixed to a flywheel to assemble a friction clutch. A pressure plate 14 is provided in the housing arrangement 12. A plurality of leaf spring arrangements 16, each of which can comprise, for example, a single leaf spring element, is provided between the housing arrangement 12 and the pressure plate 14 so that the two components can move in the axial direction with respect to each other but are essentially unable to rotate relative to each other. One end of each leaf spring arrangement 16 is fixed to a fastening section 18 on the housing arrangement 12 by means of, for example, a clinch bolt or the like, whereas the other end is fixed to a fastening section 20 on the pressure plate 16.
In pressure plate assemblies of this type, the leaf spring arrangements or leaf spring elements of the arrangements curve in the axial direction between the two attachment areas where they are connected to the housing arrangement 12 and to the pressure plate 14. This curvature is relatively pronounced especially in the case of friction clutches in which a self-reinforcing effect is provided when the force which presses the two components together is applied. The result is that line contact can be produced against the edges of the fastening sections facing in the circumferential direction, especially when the leaf spring arrangements are under load. This type of contact can lead to an increase in stress and to the rapid fatigue of the leaf spring arrangements in these areas.
The object of the present invention is to design a pressure plate assembly of the general type in question such that the leaf spring arrangement or arrangements of the assembly are protected from excessive loads in the areas where they are connected to the pressure plate arrangement and to the housing arrangement.
According to a first aspect of the invention, this object is achieved by a friction clutch, comprising a housing arrangement and a pressure plate arrangement, which is held by at least one leaf spring arrangement with freedom of movement in the axial direction relative to the housing arrangement. The at least one leaf spring arrangement is fixed by a first attachment area to a first fastening area on the pressure plate arrangement and by a second attachment area to a second fastening area on the housing arrangement.
It is also provided that the end of the first fastening area and/or of the second fastening area curves away from the minimum of one leaf spring arrangement at a certain point along the length of the at least one leaf spring arrangement.
By curving the fastening area away from its associated leaf spring arrangement, the exertion of pressure along a line is avoided, especially during transitions between unloaded and loaded states of the leaf spring arrangement, because the leaf spring arrangement can come to rest gradually against the curved surface area.
It is can be provided, for example, that the section of the length of the minimum of one leaf spring arrangement near its end is curved, and that the first fastening area and/or the second fastening area curves in the same direction.
In order to arrive at the stress-relief effect described above even while the leaf spring arrangement is still being held in a defined position, it is proposed that the end of the first fastening area and/or of the second fastening area, starting from a surface extending essentially parallel to the surface of the first attachment area and/or of the second attachment area, curves gradually away from the minimum of one leaf spring arrangement.
Especially when housing arrangements or pressure plate arrangements of very high manufacturing precision can be provided, i.e., when there is no need for any finish machining to obtain a specified thickness, for example, it can be provided that the end of the first fastening area and the end of the second fastening area are formed by integral sections of the pressure plate arrangement and of the housing arrangement, respectively. As an alternative, it is also possible for the ends of the first and second fastening areas to be formed on support elements fixed in place relative to the pressure plate arrangement and the housing arrangement, respectively.
According to another embodiment of the present invention, the object indicated above is achieved by a pressure plate assembly for a friction clutch, comprising a housing arrangement and a pressure plate arrangement, which is held by at least one leaf spring arrangement with freedom of movement in the axial direction relative to the housing arrangement. The at least one leaf spring arrangement is fixed by a first attachment area to a first fastening area on the pressure plate assembly and by a second attachment area to a second fastening area on the housing arrangement.
It also provided according to the invention that a length of the minimum of one leaf spring arrangement situated near the first fastening area curves away from the first fastening area and/or that a length of the minimum of one leaf spring arrangement situated near the second fastening area curves away from the second fastening area.
Curving the leaf spring arrangement away from its associated fastening area has the same result as before, namely, that, even during the transition to a loaded state, the pressure exerted by the leaf spring arrangement and the housing arrangement or the pressure plate arrangement on each other is not concentrated along a zone of linear contact.
So that the desired curved configuration of the leaf spring arrangement can be provided especially in applications with self-reinforcing pressure plate assemblies, it is proposed that a length of the minimum of one leaf spring arrangement following the length which curves away from the first fastening area or the second fastening area, curves in the opposite direction.
In accordance with another aspect of the present invention, the task described above is accomplished by a pressure plate assembly for a friction clutch, comprising a housing arrangement and a pressure plate arrangement, which is held by at least one leaf spring arrangement with freedom to move in the axial direction relative to the housing arrangement. The at least one leaf spring arrangement is fixed by a first attachment area to a first fastening area on the pressure plate assembly and by a second attachment area to a second fastening area on the housing arrangement.
It is also provided that, in the first attachment area and/or in the second attachment area, the minimum of one leaf spring arrangement is connected to the pressure plate arrangement or to the housing arrangement at an acute angle relative to a plane essentially perpendicular to the rotational axis of the pressure plate.
In this embodiment, therefore, at least one of the attachment areas of the leaf spring arrangement is installed at an angle from the very beginning, so that, on transitions between the unloaded and loaded states, the deformation which occurs and thus also any possible linear pressure which may also occur can be reduced.
In an embodiment of this type, it preferable for the minimum of one leaf spring arrangement to be essentially free of curvature at least in the unloaded state.
To obtain the angled mounting position, it is possible, for example, to provide at least one contact element with a contact surface extending at an acute angle to the plane in the first fastening area and/or in the second fastening area. This angled mounting position can also be obtained, for example, by designing the minimum of one contact element as an integral part of its associated fastening area. In this case, it is also preferable to provide a contact element with a contact surface extending at angle to the plane on both sides of the leaf spring arrangement in the first fastening area and/or in the second fastening area. In an embodiment of this type, which is especially advantageous with respect to fabrication and also assembly, it is also possible for the two contact elements to be in the form of slots, angled with respect to the plane, in the associated fastening area.
In the pressure plate assembly according to the invention, the minimum of one leaf spring arrangement can comprise one leaf spring element. It is preferable, furthermore, that the minimum of one leaf spring arrangement comprise one leaf spring element. As already explained above, an arrangement of this type is advantageous especially when it is desired to obtain a self-reinforcing clutch characteristic.
The present invention also pertains to a friction clutch in which a pressure plate assembly according to the invention is provided.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.